How to Play

Although the normal size of a Go board is 19 by 19 lines, it
is possible to use smaller sizes. A quick game can be played on a
13 by 13 board without losing the essential character of the
game. The following examples all use a 9 by 9 board.

We recommend that beginners learn the
basics on a 9 by 9 board, moving up to a 13 by 13 board after a few games and only playing on a 19 by 19 board if you can play
a complete game within 15 minutes and are comfortable with some of the strategic concepts.

These images show boards at different sizes - the dots are the handicap points (see below)

A game of Go starts with an empty board. Each player has an effectively
unlimited supply of pieces (called stones), one taking the black stones, the other taking white.
The main object of the game is to use your stones to form territories by surrounding
vacant areas of the board. It is also possible to capture your opponent's
stones by completely surrounding them.

Players take turns, placing one of their stones on a vacant point at each
turn, with Black playing first. Note that stones are placed on the intersections of
the lines rather than in the squares and once played stones are not moved. However
they may be captured, in which case they are removed from the board, and kept by
the capturing player as prisoners.

Diagram 1

At the end of the game, the players count one point for each vacant point inside
their own territory, and one point for every stone they have captured. The
player with the larger total of territory plus prisoners is the winner.

Diagram 1 shows the position at the end of a game on a 9 by 9 board, during
which Black captured one white stone at a.

Black has surrounded 15 points of territory, 10 in the lower right corner and 5
towards the top of the board. Black's territory includes the point a formerly
occupied by the white stone Black has captured. Adding this prisoner, Black has a total of
16 points.

The empty points which are horizontally and vertically
adjacent to a stone, or a solidly connected string of stones, are
known as liberties. An isolated stone or solidly connected string
of stones is captured when all of its liberties
are occupied by enemy stones.

Diagram 2

Diagram 3

Diagram 4

Diagram 2 shows three isolated white stones with their liberties marked by
crosses. Stones which are on the edge of the board have fewer liberties
than those in the centre of the board. A single stone on the side has
three liberties, and a stone in the corner has only two liberties.

Diagram 3 shows the same three stones of Diagram 2 each with only one liberty
left and therefore subject to capture on Black's next turn. Each of these white
stones is said to be in atari, meaning they are about to be captured.

Diagram 4 shows the position which would arise if Black went on to play at
b in Diagram 3. Black has taken the captured stone from the board, and in a real
game would keep it as a prisoner. The same remarks would apply to the
other two white stones, should Black play at c or d in Diagram 4.

Diagram 5

Strings

Stones occupying adjacent points constitute a solidly
connected string. Two examples of such solidly connected
strings of stones are shown in Diagram 5. It is
important to remember that only stones which are
horizontally or vertically adjacent are solidly connected;
diagonals do not count as connections. Thus,
for example, the two marked black stones in the top
left of Diagram 5 are two separate strings, not a single one.

Several strings close together, which belong to the same player, are often described as a group. So these two strings form a group.

Diagram 6

Diagram 7

Capturing strings

As far as capturing is concerned, a string
of stones is treated as a single unit. As with isolated stones,
a string is captured when all of its liberties are occupied by
enemy stones.

In Diagram 6 the strings of Diagram 5 have both been
reduced to just one liberty. Note that the black string in
the top right is not yet captured because of the internal
liberty at f. The two stones at the top left of Diagram 6
can each be captured independently at g or h.

In Diagram 7 we see the position which would result if
Black captured at e and White captured at f and at
g. The remaining black stone could be captured at h.
As with the capture of a single stone, the points formerly occupied
by the black string have become white territory, and vice versa.

A player may not self-capture, that is
play a stone into a position where it would
have no liberties or form part of a string
which would thereby have no liberties,
unless, as a result, one or more of the
stones surrounding it is captured.

Diagrams 8 and 9 illustrate the rule governing self-capture.
In Diagram 8, White may not play at i or j, since either
of these plays would be self-capture; the stones would
then have no liberties. However, if the outside liberties
have been filled, as shown in Diagram 9, then the plays at
i and j become legal; they fill the last black liberty in
each case, and result in the black stones being captured and
removed from the board as White's prisoners.

In Diagram 9, White was able to play at i and j because
these plays result in the capture of the adjacent black stones.
Since White's plays capture some stones, they do not
count as self-capture.

A different situation is shown in Diagram 10. The black
string here could only be captured if White were able to
play at both m and n. Since the first of these plays would be
self-capture, there is no way that White can carry out the
capture. These two separate spaces within the group are
known as eyes.

Any string or group of stones which has two or more eyes
is permanently safe from capture and is referred
to as a live string or live group. Conversely, a string of stones
which is unable to make two eyes, and is cut off
and surrounded by live enemy strings, is called a
dead string since it is hopeless and unable to avoid
eventual capture.

Diagram 11

In Diagram 11, the black string at the bottom is in
danger of being captured. To ensure that Black's string has
two eyes, Black needs to play at o. If White plays at o,
the black string will no longer be able to make two eyes,
and cannot avoid eventual capture; White can always fill
in the outside liberties and then play at p and at q. Black
plays at p or q would only hasten the string's death.

The black string at the top left of Diagram 11 is already
alive even though there is a White stone inside one of its
eyes. Since White can never capture the black stones, the
White stone caught inside the string cannot be saved.

In the course of a real game, players are not obliged to complete the capture of an
isolated dead string once it is clear to both players that the string is dead. We call this a hopeless string. In
Diagram 11, once White has played at o, the situation may be left as
it is until the end of the game. Then, the hopeless strings are simply removed from the
board and counted together with the capturing player's other prisoners.

At the top of Diagram 12, Black can capture a stone by
playing at r. This results in the situation at the top of
Diagram 13. However, this stone is itself vulnerable to
capture by a White play at u in Diagram 13. If White
were allowed to recapture immediately at u, the
position would revert to that in Diagram 12, and there
would be nothing to prevent this capture and recapture
continuing indefinitely. This pattern of stones is
called ko - a Japanese term meaning eternity. Two other
possible shapes for a ko, on the edge of the board and in
the corner, are also shown in this diagram.

Diagram 13

The ko rule removes this possibility of indefinite repetition
by forbidding the recapture of the ko, in this case
a play at u in Diagram 13, until White has made at
least one play elsewhere. Black may then fill the ko,
but if Black chooses not to do so, instead answering
White's intervening turn elsewhere, White is then permitted
to retake the ko. Similar remarks apply to the
other two positions in these diagrams; the corresponding
plays at w and v in Diagram 13 must also be delayed
by one turn.

Usually a string which cannot make two eyes will die
unless one of the surrounding enemy strings also lacks
two eyes. This often leads to a race to capture, but can
also result in a stand-off situation, known as seki, in
which neither string has two eyes, but neither can
capture the other due to a shortage of liberties. Two
examples of seki are shown in Diagram 14. Neither
player can afford to play at x, y or z,
since to do so would enable the other to make a capture.

The end of the game

When you think you can't gain any more territory, reduce your opponent's territory or capture more strings, instead of playing a stone on the board you pass and hand a stone to your opponent as a prisoner. A Black pass followed by a White pass ends the game (since Black played first, White must play last).

Any hopeless strings are removed and become prisoners. If you cannot agree whether a string is dead or not, then continue playing; you can then complete the capture of the disputed strings or confirm they are alive. (Playing after such a continuation does not change the score as each pass gives up a prisoner.)

Now you know how to play. However there are a few other things you should know:

As remarked in the introduction, one of the best features of the game of Go is its
handicap system. A weaker player may be given an advantage of anything up to
nine stones. These are placed on the board in lieu of Black's first turn.
Once all the handicap stones have been placed in position it is White's turn to play.

Through the grading system, any two players can easily establish the difference
in their strength, and therefore how many stones the weaker player should take in
order to compensate for this difference. Since a player's grade is measured
in terms of stones, the number of stones for the handicap is simply the difference
in grade between the two players.

There is an established pattern for the placement of handicap stones, shown
by the dots which are marked on any Go board. This is shown
in Diagram 15 (Black is facing the board from the bottom).

Black has a natural advantage in playing first. So in games between players of the same
strength, it is usual to compensate White for the disadvantage of playing second by adding
points to White's score. These points are called komi. From experience the value of playing first
is about 7 points, so this is the normal size of komi.
In tournaments, komi is often set at 7.5 points to avoid draws.